Correct encryption types SSL/TLS and STARTTLS

Previously EncryptionTLS correspond to STARTTLS and EncryptionSSL correspond to SSL/TLS.

To avoid confusion in names, two new const were created:

- EncryptionSTARTTLS for STARTTLS
- EncryptionSSLTLS for SSL/TLS

EncryptionTLS and EncryptionSSL are deprecated and will be removed in future.

README.md

@@ -116,7 +116,7 @@ func main() {
 	server.Port = 587
 	server.Username = "[email protected]"
 	server.Password = "examplepass"
-	server.Encryption = mail.EncryptionTLS
+	server.Encryption = mail.EncryptionSTARTTLS
 
 	// Since v2.3.0 you can specified authentication type:
 	// - PLAIN (default)

email.go

@@ -77,13 +77,17 @@ type Encryption int
 const (
 	// EncryptionNone uses no encryption when sending email
 	EncryptionNone Encryption = iota
-	// EncryptionSSL sets encryption type to SSL/TLS when sending email
+	// EncryptionSSL: DEPRECATED. Use EncryptionSSLTLS. Sets encryption type to SSL/TLS when sending email
 	EncryptionSSL
-	// EncryptionTLS sets encryption type to STARTTLS when sending email
+	// EncryptionTLS: DEPRECATED. Use EncryptionSTARTTLS. sets encryption type to STARTTLS when sending email
 	EncryptionTLS
+	// EncryptionSSLTLS sets encryption type to SSL/TLS when sending email
+	EncryptionSSLTLS
+	// EncryptionSTARTTLS sets encryption type to STARTTLS when sending email
+	EncryptionSTARTTLS
 )
 
-var encryptionTypes = [...]string{"None", "SSL/TLS", "STARTTLS"}
+var encryptionTypes = [...]string{"None", "SSL/TLS", "STARTTLS", "SSL/TLS", "STARTTLS"}
 
 func (encryption Encryption) String() string {
 	return encryptionTypes[encryption]
@@ -775,7 +779,7 @@ func dial(host string, port string, encryption Encryption, config *tls.Config) (
 
 	// do the actual dial
 	switch encryption {
-	case EncryptionSSL:
+	case EncryptionSSL, EncryptionSSLTLS:
 		conn, err = tls.Dial("tcp", address, config)
 	default:
 		conn, err = net.Dial("tcp", address)
@@ -814,12 +818,12 @@ func smtpConnect(host, port, helo string, a auth, encryption Encryption, config
 		return nil, fmt.Errorf("Mail Error on Hello: %w", err)
 	}
 
-	// start TLS if necessary
-	if encryption == EncryptionTLS {
+	// STARTTLS if necessary
+	if encryption == EncryptionTLS || encryption == EncryptionSTARTTLS {
 		if ok, _ := c.extension("STARTTLS"); ok {
 			if err = c.startTLS(config); err != nil {
 				c.close()
-				return nil, fmt.Errorf("Mail Error on Start TLS: %w", err)
+				return nil, fmt.Errorf("Mail Error on STARTTLS: %w", err)
 			}
 		}
 	}

example/example_test.go

@@ -170,7 +170,7 @@ func TestWithTLS(t *testing.T) {
 	client.Port = 587
 	client.Username = "[email protected]"
 	client.Password = "asdfghh"
-	client.Encryption = mail.EncryptionTLS
+	client.Encryption = mail.EncryptionSTARTTLS
 	client.ConnectTimeout = 10 * time.Second
 	client.SendTimeout = 10 * time.Second
 
@@ -198,7 +198,7 @@ func TestWithSSL(t *testing.T) {
 	client.Port = 465
 	client.Username = "[email protected]"
 	client.Password = "asdfghh"
-	client.Encryption = mail.EncryptionSSL
+	client.Encryption = mail.EncryptionSSLTLS
 	client.ConnectTimeout = 10 * time.Second
 	client.SendTimeout = 10 * time.Second